Let's look at another spot. I'll hover my mouse over an area on his back:

That area looks pretty green to me, and if we look at what the Info palette is telling us:

Sure enough, green is by far the predominant color, coming in at a value of 180. The red is only showing up at 20, which is a very small amount, and the blue is even less at 16.

Let's do this one more time. I'll hover the mouse somewhere over the bird's head:

This time, the blue should be making a much stronger showing in the Info Palette:

And sure enough, this time the blue is coming in at a value of 208 and is the predominant color. Of course, the bird's head isn't pure blue. It's more of a purple-blue, which explains why green is still coming in at 100, and even red is making a decent appearance at a value of 90. All three are mixing together on the screen to give us that purple-blue color we're seeing.

I could continue hovering my mouse over any spot in the photo (I won't, but I could) and we'd see the values for red, green and blue changing in the Info palette, since every single color in the image is being made up of some combination of them.

And that's how the RGB color mode works. Again, RGB stands for nothing more difficult than "Red", "Green" and "Blue", and because this image is in the RGB color mode, Photoshop is reproducing every one of the colors using combinations of red, green and blue.

Next we'll look at the second part of this tutorial, color channels.